Research on Numerical Simulation of Aerodynamic Noise in Split Air-conditioning Evaporation Uint of Rail Vehicle

A computational fluid dynamics model of split air-conditioning evaporation unit is established. The transient flow field of air flow is calculated by large eddy simulation, the frequency domain data of air flow field are obtained by FFT of transient flow field data. Basing on the frequency domain data of flow field, the aerodynamic noise of evaporation unit is calculated through the boundary element method, the calculated results are compared with the test results, the calculated result is only 1.46 dB different from the test result. The result of research shows that the noise value of the outlet of evaporation unit is the highest, and the loudest pressure level is higher than 56 dB; loudest power level occur in the 125Hz to 400Hz low frequency band. Although the sound power level gradually decreases with the increase of frequency, the high frequency band at 5000Hz still radiates more than 55dB sound power level. This indicates that the aerodynamic noise of the air-conditioning evaporation unit belongs to broadband noise.